JP2821295B2 - Tool components with excellent fracture resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a covering member for a cutting tool subjected to a large impact load and a tool requiring wear resistance, and more particularly to a covering member suitable for a cutting tool used as a throw-away tip.

[0002]

2. Description of the Related Art In order to improve the wear resistance of a cemented carbide tool, a ceramic-based wear-resistant coating has been conventionally formed on the surface of the tool. For example, TiC—Ti (C, N) —Al ₂ is formed on the surface of a WC-based cemented carbide by chemical vapor deposition (CVD) or physical vapor deposition (PVD).
When a ceramic such as O ₃ is coated, the wear resistance is significantly improved. However, when used for a cutting tool that receives a large impact load such as intermittent cutting, the fracture resistance is inferior to that of a cemented carbide that is not coated as described above, so that there is a limitation in use.

[0003] As to the cause of the decrease in fracture resistance due to such coating, the theory that defects such as voids generated at the time of vapor deposition serve as a starting point of fracture and the theory that the fracture strength of the as-deposited ceramic film is small. Although improvements in the film formation method and examination of the film formation conditions and post-treatment conditions have been made, sufficient effects have not been achieved.

[0004] One of the causes of the inferior fracture resistance of such coated cemented carbide is that CVD coating performed at a high temperature of, for example, 1,100 ° C depends on the difference in thermal expansion coefficient between the cemented carbide of the base material and the ceramic coating. In the course of cooling after the treatment, we focused on reducing the fracture resistance by generating tensile residual stress in the coating, and increasing the Co content of the base material near the interface of the coating to suppress the propagation of fracture cracking Method (Hayashi et al., Powder and Powder Metallurgy, Vol. 32, No. 7, page 278 (1985); Asai et al., Precision Machinery, October 45, 1981), method of increasing WC particle size (Kobori et al., Powder and Powder Metallurgy) ,
Vol. 36, No. 2, 130 pages (1989), Plasma CV
D (Doi et al., The same journal, Vol. 33, No. 8, pp. 413 (1986)) and the like have been reported, but their effects are still insufficient.

Further, as a novel method for relaxing the above-mentioned tensile residual stress, a film having a width of 5 μm or less and an interval of 10 to 20 μm is provided.
It has been proposed to release the residual tensile stress by generating cracks of 0 μm (in all cases, the average value) (Katayama et al., JP-A-3-92204; Katayama et al., Bulletin of the Japan Institute of Metals, Vol. 30, No. 4, 298-300 pages (199
1)), a considerable effect is obtained. However, depending on the use of the tool and the conditions of use, higher fracture resistance may be required in addition to wear resistance.

That is, the shape of the workpiece is becoming more and more complicated year by year, and the number of occasions of intermittent cutting receiving a large impact load is increasing. Further, advanced cutting and heavy cutting have been demanded, and development of tools and members thereof having more excellent fracture resistance and wear resistance has been desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of forming a coating on a base material made of a metal (including a sintered alloy), a cermet or a ceramic sintered body and remaining in a coating of a tool member. An object of the present invention is to improve the peeling resistance of the film by removing the existing tensile stress to make the film state having almost no tensile stress. It is a further object of the present invention to provide a tool member having improved wear resistance and chipping resistance.

[0008]

Means for Solving the Problems As a result of repeated studies to achieve the above object, the present inventors have found that the object can be achieved by further reducing the crack interval, and the present invention has been achieved. It was completed.

That is, the tool member of the present invention having excellent fracture resistance is a tool member having a hard coating formed on the surface of a metal, cermet or ceramic sintered body, wherein the hard coating is subdivided by cracks. And the average value of the crack intervals on the surface of the hard coating that has been subdivided is 0.1.
It is not less than 1 μm and less than 5.0 μm.

The base material in the tool member of the present invention is a metal,
It is made of cermet or ceramic sintered body. The metal can be a single metal or an alloy, tungsten, molybdenum,
Examples include high melting point metals such as titanium; and alloys such as high speed steels such as tungsten based and molybdenum based. As cermet, WC-Co system used as cemented carbide,
WC-TiC-Co system, WC-TiC-TaC-Co
System, TiC-Ni or TiC-TiN-Ni (Co) system, and the like. As a ceramic sintered body, W
C, TiC, TiN, SiC, Si ₃ N ₄ , ZrO ₂ ,
A ceramic sintered body mainly containing Al ₂ O ₃ or the like is exemplified. Of these, cermets such as cemented carbide are particularly preferred.

In the present invention, the hard coating formed by coating the surface of the base material includes metals of Group 4a, 5a and 6a of the periodic table, carbides, nitrides and oxides of Al and Si, and carbonitrides. Such mutual solid solutions are exemplified. It is preferable to be made of one or more selected from carbides, nitrides and carbonitrides of Ti, Zr, Hf, Nb, Ta, Cr and Mo, and Al ₂ O ₃ .

Such a coating may be a single layer or a plurality of layers, for example, two to four layers. In order to reduce the stress resulting from the difference in the coefficient of thermal expansion between the substrate and the outermost layer, it is preferable to provide one or more intermediate layers having an intermediate coefficient of thermal expansion between the two layers.

Further, such a coating may be provided on the entire surface of the base material, or may be provided only on a part of the surface such as a cut portion requiring abrasion resistance.

Such a film can be formed by a known method such as CVD.

A feature of the present invention is that at least the surface of the hard coating is subdivided by fine cracks, and the average value of the crack interval is 0.1 μm or more.
The thickness is less than 5.0 μm, preferably 0.5 to 4.5 μm. By providing cracks at such intervals, it becomes possible to effectively remove the residual tensile stress. When the crack interval is 5.0 μm or more, the effect is small when a large impact force is applied as in the case of using as a milling tool, for example, and the effect is reduced to 0.1 μm.
If it is less than 30, the coating is easily peeled off.

The average value of the crack width is preferably 2 μm or less. If the width of the crack exceeds 2 μm, the abrasion resistance decreases.

The crack depth may reach the interface between the coating and the substrate, and the crack may penetrate slightly into the inside of the substrate, for example, into the substrate to a depth of 5 μm or less.

The portion where such cracks are formed may be the entire surface on which the hard coating is applied, but it is more preferable to form the crack in a portion requiring fracture resistance, for example, in a portion of the scooping surface in contact with chips. This is preferable because the property is not impaired and the energy required for crack formation is small.

Such fine cracks can be formed by a method such as laser beam irradiation, infrared beam irradiation, ultrasonic waves, or peeling with a metal or nonmetal sphere. When laser beam irradiation is used, the adhesion state of the interface between the base material and the hard coating is not affected during crack formation, so that the coating does not peel off under subsequent use conditions. Therefore, even if the crack interval is reduced, the wear resistance does not decrease. YA in laser beam
When irradiation is performed using a G laser under the following irradiation conditions, for example, irradiation energy of 100 kW or less, preferably 50 kW or less; spot size of 0.5 mm or less, preferably 0.2 mm or less, peeling of the coating may occur. It is particularly preferable because it hardly occurs and has excellent wear resistance and chipping resistance.

[0020]

According to the present invention, the hard coating formed on a part or the whole of the surface of the base material of the tool member is subdivided into cracks at an average interval of 0.1 μm or more and less than 5.0 μm, thereby obtaining the hard coating. Almost all tensile residual stress in the coating can be eliminated. By almost eliminating the residual tensile stress in the coating in this way, there is no starting point of causing a defect such as a fracture crack in the coating, and the propagation of the fracture crack into the inside of the base material can be suppressed.

[0021]

According to the present invention, the present invention provides a tool coating member excellent in chipping resistance while maintaining wear resistance by a hard coating having excellent peeling resistance formed on the surface according to the present invention. Can be.

Since the tool member of the present invention has wear resistance and chipping resistance as described above, cutting tools such as cutting tools, milling tools, drills and end mills; or slitters, guide rolls, nozzles, etc. It is useful as a member of a wear-resistant tool. Particularly suitable as a member of a cutting tool used as a throw-away insert.

As described above, the present invention has solved the problem of fracture resistance which is a drawback of the conventional coated cemented carbide tool member.

[0024]

The present invention will be described below with reference to examples and comparative examples. The present invention is not limited by these examples. In these examples, the percentages of the composition are by weight
Is shown.

Examples 1 to 5 On a surface of a base material made of a cemented carbide having a composition of 84% WC-8% (W, Ta, Ti) C-8% Co, a TiC film was formed by CVD, and a Ti (C , N) film and Al ₂ O ₃ film are sequentially formed, each having a three-layer structure, and having a film thickness of Table 1.
As shown in FIG. 5, five coated cemented carbide tips having different hard coatings in the form of throw-away tips were obtained.

A portion of the scooped surface of the coated cemented carbide obtained in this way, which was in contact with the chips, was irradiated with a YAG laser beam. The irradiation condition is irradiation energy 1
0-50 kW, spot diameter varied between 0.1-0.2 mm. As a result of the laser beam irradiation, five coated cemented carbide cutting tool member samples having cracks formed in the irradiated portions were obtained.

The average value of the intervals between the cracks thus formed was measured by a metal micrograph. That is,
Find the number of cracks that exist for a certain distance from the photos,
The distance was divided by the number obtained by subtracting 1 from the number of cracks to obtain an average value of crack intervals. Table 1 shows the average values of the crack intervals thus obtained.

The cutting test under the following conditions (A) and (B), that is, the fracture resistance test and the wear resistance, was performed using the tool member sample obtained by subdividing a part of the hard coating by cracking in this manner. A sex test was performed.

(A) Fracture resistance test (dry cutting) Tip shape: SPKN42STR Work material: S48C (HB200-240, diameter 120m)
m, length 700mm) Cutting speed: 150m / min Feed: 0.2mm / rev Depth of cut: 1.5mm Evaluation: Number of impacts until chipping or chipping

(B) Abrasion resistance test (wet cutting) Tip shape: SPKN42STR Work material: S48C (HB230-250, diameter 170m)
m, length 750 mm) Cutting Speed: 150 meters / min Feed: 0.25 mm / rev cut: 2.0 mm Evaluation: average flank wear (V _B) cutting time until the 0.3 mm (min)

Table 1 shows the test results.

[0032]

[Table 1]

Comparative Examples 1 to 5 The same substrates as those used in Examples 1 to 5 were used.
The same three layers of coatings as those provided in Example 1 were sequentially formed to the thicknesses shown in Table 1 by the CVD method.
Thus, five coated cemented carbide tips having the same shape as in Example 1 were obtained.

A steel ball having a diameter of 0.3 mm was projected onto the surface of the coating of these cutting tool members by the shot peening method to obtain a cutting tool member sample in which cracks were formed on one surface of the coating. The projection conditions were varied between a projection speed of 50 to 80 m / s and a projection time of 1 to 5 min.

The distance between cracks was measured in the same manner as in Examples 1 to 5, and a cutting test was performed in the same manner. The result is
Table 1 shows a comparison with Examples 1 to 5.

Example 6 and Comparative Example 6 A commercially available Si ₃ N ₄ sintered body was used as a base material, and a 1 μm thick TiN film and a 3 μm thick Al ₂ O ₃ were formed on the surface by CVD. A film and a 0.5 μm-thick TiN film were sequentially formed to obtain two coated cemented carbide tips.

One of them has an irradiation energy of 50 k
W, YAG laser beam irradiation was performed under irradiation conditions of a spot diameter of 0.2 mm to obtain a cutting tool member sample having a crack interval of 2.5 μm (Example 6). Also, in the other one,
Shot peening with a steel ball having a diameter of 0.3 mm at a projection speed of 60 m / s and a projection time of 3 min.
A 1.8 μm cutting tool member sample was obtained (Comparative Example 6).
Using these samples, cutting tests were performed under the following condition (C).

(C) Milling cutting test (dry cutting) Chip shape: SNMN120408 Work material: FCD60 (45 mm × 200 mm) Cutting speed: 150 m / min Cutting depth: 1.5 mm Evaluation: Starting from a feed of 0.20 m / rev, If there is no loss, the feed is increased in increments of 0.03 mm / rev, and the feed with the loss is evaluated.

As a result, the sample of Comparative Example 6 was 0.23 mm / r
While the sample was broken at the feed of ev, the sample of Example 6 had a defect at the feed of 0.38 mm / rev for the first time.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayuki Hashimura 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Headquarters (72) Inventor Tsune Sasaki 1-7 Tsukakoshi, Sachi-ku, Kawasaki-shi, Kanagawa Address Toshiba Tungaloy Co., Ltd. (72) Inventor Toshiaki Takahashi 1-7-7 Tsukagoshi, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Tungaloy Co., Ltd. (72) Inventor Masahiro Higuchi 64-36 Aze, Nippon Steel Inside Carbide Co., Ltd. (72) Inventor Tetsuro Sawashima 26-5 Ikeda Nishimachi, Neyagawa City, Osaka Prefecture Inside Toho Metal Co., Ltd. (56) References JP-A-63-38565 (JP, A) JP-A-64-31972 (JP, A) JP-A-3-92205 (JP, A) JP-A-4-8409 (JP, A) JP-A-4-164504 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) B23B 2 7/14

Claims (3)

(57) [Claims] 1. A tool member having a hard coating formed on a surface of a metal, cermet, or ceramics sintered body, wherein the hard coating is subdivided by cracks, and the surface of the subdivided hard coating is A tool member having excellent fracture resistance, wherein an average value of crack intervals is 0.1 μm or more and less than 5.0 μm. 2. The tool member according to claim 1, wherein the hard coating is formed on a part of the surface of the substrate. 3. The tool member according to claim 1, wherein the base material is a cemented carbide.